The Collaborative International Dictionary of English v.0.48:

Participle \Par"ti*ci*ple\, n. [F. participe, L. participium,
   fr. particeps sharing, participant; pars, gen. partis, a part
   + capere to take. See Participate.]
   1. (Gram.) A part of speech partaking of the nature of both
      verb and adjective; a form of a verb, or verbal adjective,
      modifying a noun, but taking the adjuncts of the verb from
      which it is derived. In the sentences: a letter is
      written; being asleep he did not hear; exhausted by toil
      he will sleep soundly, -- written, being, and exhaustedare
      participles.
      [1913 Webster]

            By a participle, [I understand] a verb in an
            adjectival aspect.                    --Earle.
      [1913 Webster]

   Note: Present participles, called also imperfect, or
         incomplete, participles, end in -ing. Past participles,
         called also perfect, or complete, participles, for the
         most part end in -ed, -d, -t, -en, or -n. A participle
         when used merely as an attribute of a noun, without
         reference to time, is called an adjective, or a
         participial adjective; as, a written constitution; a
         rolling stone; the exhausted army. The verbal noun in
         -ing has the form of the present participle. See
         Verbal noun, under Verbal, a.
         [1913 Webster]

   2. Anything that partakes of the nature of different things.
      [Obs.]
      [1913 Webster]

            The participles or confines between plants and
            living creatures.                     --Bacon.
      [1913 Webster]

WordNet (r) 3.0 (2006):

participle
    n 1: a non-finite form of the verb; in English it is used
         adjectivally and to form compound tenses [syn:
         participle, participial]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "participle":
   adjectival, adjective, adverb, adverbial, adversative conjunction,
   attributive, conjunction, conjunctive adverb,
   coordinating conjunction, copulative, copulative conjunction,
   correlative conjunction, disjunctive, disjunctive conjunction,
   exclamatory noun, form class, form word, function class, gerundive,
   interjection, part of speech, particle, past participle,
   perfect participle, preposition, present participle,
   subordinating conjunction, verbal adjective